A Jacobs or like key-operated chuck can comprise a chuck body formed with a forwardly tapered face along which a plurality, usually three, chuck jaws are slidably guided so as to move together as the jaws are advanced forwardly and move apart as they are retracted, thereby enabling them to grip or release a drill shank or other tool.
A toothed ring (gear crown) is rotatably mounted on this body and operatively connected to the jaws so that its rotation relative to the body by the chuck key can tighten the jaws on the tool or enable the release of the latter. The teeth of this ring mesh with the teeth of a pinion formed on the key which can have a projection received in a bore of the chuck body and designed to position the key for proper meshing engagement of its pinion with the teeth of the ring.
The chuck structure generally also comprises a further member serving for attachment of the chuck to the threaded spindle of a machine tool or drill. This member can be provided with an internal thread in which the spindle is received.
It has been proposed, see for example German Gebrauchsmuster No. 7,241,181, to provide a sleeve which connects the ring and this latter member and which can be externally knurled or milled to; facilitate gripping when, for example, the operator wishes to mount the chuck upon the spindle or remove it therefrom. This sleeve serves to prevent axial displacement of the ring relative to the chuck body. The sleeve, in turn, is rotatable on the chuck body but should be axially immovable relative thereto.
It has been found to be advantageous to connect the toothed ring with the sleeve by providing the toothed ring with an outwardly open circumferential groove having a flank facing toward the front or shank-receiving part of the chuck and a further flank facing in the opposite direction. The ring can have a rim which is formed fittingly receiving in this groove and abuts these flanks. Assembly of the device is facilitated if the rim is at least deformed into an inwardly projecting ridge after the rim has been positioned in line with the groove. The forwardly facing flank forms a shoulder which retards axial separation of the ring from the sleeve by a forward movement of the ring or a rearward movement of the sleeve.
Advantageously, the rim of the sleeve is provided with a conical surface or taper which facilitates deformation of the sleeve to provide the ridge which sits in the groove. Thus, the sleeve can be forced over the ring until the rim abuts against the rearwardly facing flank, whereupon an inward deformation or clinching of the sleeve drives the rim into form-fitting relationship with the groove and forms the aforementioned ridge. The tool which is used for this purpose need only have the proper inclination to suitably press the sleeve into the groove.
Such chucks have been found to be highly effective, inexpensive and of low cost. Although some difficulties have been encountered in the pressing of the rim of the sleeve behind the aforementioned shoulder of the toothed ring. The difficulty is the nonreproducible seating of the rib formed by the deformation and the lack of sufficient precision of this rib. In other words, the seating of the rib within the toothed ring does not always occur with the desired degree of precision even though the same tool is used.